Dynomax's Super Turbo mufflers are the closest you can get to running an open pipe, but a lot quieter.

To make things even better, Super Turbos have more features than most other mufflers put together--
less backpressure for improved quarter mile times, aluminized construction for long life and good looks, patented flow directors that channel exhaust for maximum performance, and fiberglass matting for a deep, throaty, powerful performance tone.